Wild Potato Species Research Articles

Моделювання природної еволюції видів роду Solanum L. cекції Petota Dumort. за фітофторостійкістю

<p>The article presents the theoretical substantiation and experimental data, confirming the natural evolution of potato species from the standpoint of the stability and effectiveness of genetic control of resistance to late blight. Resistant samples of wild potato species which were differ in the appearance of the trait were used as the initial material for research. Artificial infection of seedlings obtained from self-pollination of potato samples with the race of phytophthora (<em>Phytophtora infestans </em>(Mont.) De Bary) 1-11X, Y, Z (25-30 conidia in the view of the microscope, 120 x), which made it possible to identify various types of resistance to fungus. The evolutionary changes of the species, relating their response to the changing of phytopathological situation in their areas have been experimentally proven. The intraspecific variety of <em>S. demissum </em>Lindl and <em>S. stoloniferum </em>Schlechtd. samples by resistance to phytophthora, which manifested both among I1 and among I2, has been identified. Depending on the evolution of the samples, differences in the genetic control of resistance to the pathogen were found, which was manifested in the frequency of appearance of offspring with high resistance, hypersensitivity, high, medium and low field resistance, as well as complete damage of seedlings. In the species of <em>S. demissum</em> the sample was found, in its progeny the seedlings with extremely high resistance to the pathogen were not isolated, but in the case of the UK sample No 27-19 the part of such material was 94.2%. The lower level of genetic control in this species was characterized by the type of supersensitive resistance. Variation in the offspring samples by this type of resistance was observed in the range of 0-78.4%, and the splitting of seedlings with high field stability was even smaller and was within 0-45%. Similar data were obtained for the species of <em>S. stoloniferum</em>. A similar type of conjugate evolution of phytophthora resistance in the testing species has been experimentally proved. There were no differences in the manifestation of hypersensitive resistance or they were very insignificant. The maximum differences between species were 4% in the class with the offspring frequency of 81-100%. Based on the results of the phytophthora resistance evaluation of various samples of potato species in I2, it was assumed that under epiphytotic conditions in the area of species growth, samples with effective genetic control of the trait, i.e., with an extremely high degree of resistance, will be evolutionally promising. </p>

Genomic Analyses Yield Markers for Identifying Agronomically Important Genes in Potato

Wild potato species have substantial phenotypic and physiological diversity. Here, we report a comprehensive assessment of wild and cultivated potato species based on genomic analyses of 201 accessions of Solanum section Petota. We sequenced the genomes of these 201 accessions and identified 6 487 006 high-quality single nucleotide polymorphisms (SNPs) from 167 accessions in clade 4 of Solanum section Petota, including 146 wild and 21 cultivated diploid potato accessions with a broad geographic distribution. Genome-wide genetic variation analysis showed that the diversity of wild potatoes is higher than that of cultivated potatoes, and much higher genetic diversity in the agronomically important disease resistance genes was observed in wild potatoes. Furthermore, by exploiting information about known quantitative trait loci (QTL), we identified 609 genes under selection, including those correlated with the loss of bitterness in tubers and those involved in tuberization, two major domesticated traits of potato. Phylogenetic analyses revealed a north-south division of all species in clade 4, not just those in the S. brevicaule complex, and further supported S. candolleanum as the progenitor of cultivated potato and the monophyletic origin of cultivated potato in southern Peru. In addition, we analyzed the genome of S. candolleanum and identified 529 genes lost in cultivated potato. Collectively, the molecular markers generated in this study provide a valuable resource for the identification of agronomically important genes useful for potato breeding.

Ectopic expression of StCBF1and ScCBF1 have different functions in response to freezing and drought stresses in Arabidopsis

Solanum tuberosum potato species constitute the bulk of economically and agronomically important potato production. However, S. tuberosum is a drought- and frost-sensitive species that is incapable of acclimating to the cold. Solanum commersonii is a tuber-bearing wild potato species that exhibits greater frost and drought resistance than S. tuberosum. CBF/DREB (C-REPET BINDING FACTOR/DROUGHT RESPONSE ELEMENT BINGING FACTOR) transcription factors play important roles in response to a variety of abiotic stresses, such as cold, drought and salt stresses. To explore different functions between S. tuberosum CBF1 (StCBF1) and S. commersonii CBF1 (ScCBF1), Arabidopsis was transformed with the ScCBF1 and StCBF1 genes driven by a constitutive CaMV35S promoter. Our results reveal that the ScCBF1 transgenic lines are much more tolerant to freezing and drought than the StCBF1 transgenic lines. The development of transgenic plants was altered, resulting in dwarf phenotype with delayed flowering and thicker and additional rosette leaves. The expression levels of several COR (COLD-RESPONSIVE) genes and development-related genes, including genes that inhibited plant growth (GA2ox7, RGL3) and delayed flowering (FLC) were higher in transgenic plants. These results suggest that these two potato CBF1 play important roles in the plant response to abiotic stress and can influence plant growth and development, and ScCBF1 plays a more pronounced function than StCBF1.

Evaluation of extreme resistance genes of Potato virus X (Rx1 and Rx2) in different potato genotypes

Potato (Solanum tuberosum L.) is considered as one of the most important staple foods in the world. Classical breeding for resistance to pests, pathogens and viruses involves the identification of resistance sources, which are often found in different wild potato species. Potato virus X (PVX) attacks potato worldwide, causing considerable amount of yield losses, reaching 20% of productivity depending upon the virus strain. To decrease its impact, there’s serious interest to develop new varieties carrying the Rx1 and/or Rx2 genes which originally came from the wild species Solanum tuberosum ssp. andigena and Solanum acaule, respectively; these genes are able to provide extreme resistance to PVX which could be facilitated with molecular marker-assisted selection. In this study, twenty-five potato genotypes, belong to Potato Research Center, were tested to detect the presence of Rx1 and Rx2 extreme resistance genes of PVX by using 5Rx1 and 106Rx2 specific markers, respectively, to enhance breeding efficiency for the purpose of developing new varieties. The results showed that three genotypes carried the 5Rx1 marker. On the other hand, the results with the 106Rx2 marker showed that thirteen individuals (52%) of the genotypes carried the 106Rx2 marker. Sixteen genotypes (64%) are resistant to PVX and have a great potential for gene introgression, while the other nine genotypes were not carriers of the markers. Genotypes those are carrying the markers were strongly recommending to be used by breeders to develop new PVX extreme resistance potato varieties.

Mitochondrial genome sequence of tuber-bearing wild potato, Solanum commersonii Dunal

We report two complete mitochondrial genome sequences of a tuber-bearing wild potato species (Solanum commersonii). The genomes are circular DNA molecules with lengths of 213,676 bp and 338,427 bp containing 80 nonredundant genes totally, including 34 protein-coding genes, 25 hypothetical open reading frames, 18 tRNA genes, and 3 rRNA genes. Phylogenetic analysis using common protein-coding sequences confirmed that S. commersonii belongs to the Solanoideae subfamily in the Solanaceae family.

Late blight resistance status in wild potato species against Indian population of Phytophthora infestans

Late blight caused by oomycete pathogen Phytophthora infestans is the most destructive disease affectingpotato crop world-wide with losses up to 90% in India. Resistant varieties offers safe and economical mean formanagement of the disease. Wild species of potato are the reservoirs of resistance against many insect pestand diseases including late blight. In the present study, 539 clones of 91 potato accessions belonging to 18wild species maintained at CPRI, Shimla were evaluated for presence of durable resistance against late blight. The clones SS 1764–19 (S. alandiae), SS 1763–09 and SS 1763–25 (S. albicans), SS 1769–04, SS 1769–08 and SS 1770–14 (S. arnezii), SS 1784–07 (S. berthaultii), SS 1794–07 (S. brevicaule), SS 0551-02, SS 0680-06, SS 1671–01 and SS 1671–03 (S. chacoense), SS 1835, SS 1846–05, SS 1847–09, SS 1850-0, SS 1850–01 and SS 1850–04 (S. demissum), SS 1926–09, SS 1926–10, SS 1926–11 and SS 1926–13 (S. microdontum), SS 2615–01, SS 2616–01, SS 2616–02, SS 2655–01, SS 2656–02, SS 2658–01, SS 2658–02 and SS 2658–03 (S. pinnatisectum), SS 1664–02 and SS 1724–40 (S. sparsipilum), SS 2038–04 and SS 2048-0 (S. tuberosum ssp. andigena) and SS 2082-0 (S. vernei)were found to be most promising having high late blight resistance under laboratory and field testing. Althoughsome difficulties exist in direct utilization of these clones due to ploidy and EBN differences, but these can beovercome through both short and long-term breeding strategies viz., ploidy and EBN manipulation, bridgingspecies, embryo rescue, somatic hybridization and molecular techniques.

Studying the potential of the initial potato material with the aim of breeding for drought resistance

Purpose . To evaluate and select hybrids, varieties of the parental nursery of the breeding process, biotechnological lines and wild species of potato for physiological parameters of drought resistance. Methods . Physiological and biochemical, selection ones, statistical data processing. Results . The data is given concerning the evaluation of the water retaining and water regeneration capacity of potato leaves of promising hybrids of competitive and ecological test, varieties of the parental nursery, biotechnological lines and wild species and their integral indicator of drought resistance. The studied samples were grown in the nurseries of field selection crop rotation. Accordingly, the initial material with the highest drought resistance value has been defined. Among the evaluated material, eight hybrids of the competitive and ecological test have been selected (drought resistance coefficient was ranging from 59.4% to 84.8%) and five biotechnological lines of ‘Hlazurna’ and ‘Dorohin’ varieties (drought resistance coefficient was in the range of 55.5% to 67.5%). As for wild species, almost half of the samples (47.8%) were characterized by a high coefficient of drought resistance (from 55 to 78%). Selected samples with high values of drought resistance were recommended to use as a source and drought resistance donors when creating new potato varieties. Conclusions . The initial potato material (hybrids, varieties, biotechnological lines and wild species) with high values of drought resistance (55.0–84.8%) has been selected. These samples are recommended to use in the breeding process when creating new drought resistance potato varieties.

The Biology and Phylogenetics of Potato virus S Isolates from the Andean Region of South America.

Biological characteristics of 11 Potato virus S (PVS) isolates from three cultivated potato species (Solanum spp.) growing in five Andean countries and 1 from Scotland differed in virulence depending on isolate and host species. Nine isolates infected Chenopodium quinoa systemically but two others and the Scottish isolate remained restricted to inoculated leaves; therefore, they belonged to biologically defined strains PVSA and PVSO, respectively. When nine wild potato species were inoculated, most developed symptomless systemic infection but Solanum megistacrolobum developed systemic hypersensitive resistance (SHR) with one PVSO and two PVSA isolates. Andean potato cultivars developed mostly asymptomatic primary infection but predominantly symptomatic secondary infection. In both wild and cultivated potato plants, PVSA and PVSO elicited similar foliage symptoms. Following graft inoculation, all except two PVSO isolates were detected in partially PVS-resistant cultivar Saco, while clone Snec 66/139-19 developed SHR with two isolates each of PVSA and PVSO. Myzus persicae transmitted all nine PVSA isolates but none of the three PVSO isolates. All 12 isolates were transmitted by plant-to-plant contact. In infective sap, all isolates had thermal inactivation points of 55 to 60°C. Longevities in vitro were 25 to 40 days with six PVSA isolates but less than 21 days for the three PVSO isolates. Dilution end points were 10-3 for two PVSO isolates but 10-4 to 10-6 with the other isolates. Complete new genome sequences were obtained from seven Andean PVS isolates; seven isolates from Africa, Australia, or Europe; and single isolates from S. muricatum and Arracacia xanthorhiza. These 17 new genomes and 23 from GenBank provided 40 unique sequences; however, 5 from Eurasia were recombinants. Phylogenetic analysis of the 35 nonrecombinants revealed three major lineages, two predominantly South American (SA) and evenly branched and one non-SA with a single long basal branch and many distal subdivisions. Using least squares dating and nucleotide sequences, the two nodes of the basal PVS trifurcation were dated at 1079 and 1055 Common Era (CE), the three midphylogeny nodes of the SA lineages at 1352, 1487, and 1537 CE, and the basal node to the non-SA lineage at 1837 CE. The Potato rough dwarf virus/Potato virus P (PVS/PRDV/PVP) cluster was sister to PVS and diverged 5,000 to 7,000 years ago. The non-SA PVS lineage contained 18 of 19 isolates from S. tuberosum subsp. tuberosum but the two SA lineages contained 6 from S. tuberosum subsp. andigena, 4 from S. phureja, 3 from S. tuberosum subsp. tuberosum, and 1 each from S. muricatum, S. curtilobum, and A. xanthorrhiza. This suggests that a potato-infecting proto-PVS/PRDV/PVP emerged in South America at least 5,000 years ago, became endemic, and diverged into a range of local Solanum spp. and other species, and one early lineage spread worldwide in potato. Preventing establishment of the SA lineages is advised for all countries still without them.

Overcoming unilateral incompatibility in crosses with wild allotetraploid potato species Solanum stoloniferum Schldtl. & Bouchet

The germplasm of valuable for breeding wild allotetraploid potato species Solanum stoloniferum is rarely used because of pre- and postzygotic reproductive barriers with cultivated potatoes. One of the factors that complicate crosses between S. stoloniferum and S. tuberosum is unilateral incompatibility (UI). Here, we present the results of application of S. verrucosum and S v S v -lines for overcoming UI in crosses with S. stoloniferum and of generating male fertile hybrids derived from this species. S v S v -lines are F2 S. tuberosum dihaploid × S. verrucosum that are male fertile and have D/γ-type cytoplasm. Since they are homozygous for S v gene from S. verrucosum, they were expected to have the same ability for elimination of prezygotic incompatibility as this species. Three accessions of S. verrucosum and seven S v S v -lines were pollinated by 26 accessions of S. stoloniferum. The crosses with S. verrucosum failed or had low efficacy (1.5–2.4 seeds per pollination). On the other hand, use of S v S v -lines was more efficient: 15.8 seeds per pollination. In spite of low percentage of germination (1.9%), 40 seedlings of interspecific hybrids were produced. The experiment on hybridization between S v S v -lines and S. stoloniferum has been reproduced with the accession PI 205522 of the wild species, which had DNA markers of PVY and LB resistance genes and W/γ cytoplasm: 950 hybrid seeds and 12 viable seedlings were produced. The genome of the seedlings was doubled by colchicine treatment, which generated hexaploids that formed highly fertile pollen and set seeds from self-pollination. We were able to cross them as females with the variety Katahdin.

Characterization of trichome morphology and aphid resistance in cultivated and wild species of potato

Trichomes are specialized epidermal structures that protect plants from abiotic and biotic stresses. Cultivated potato (Solanum tuberosum) is known to have both glandular and non-glandular trichomes. However, the criteria for trichome type classification have not been studied in detail. In addition, there is a poor understanding of the types of trichomes that exist in wild potato species. Here, the morphology and density of trichomes were compared between a representative cultivated potato variety and 17 wild potato species using Cryo Scanning Electron Microscopy (CryoSEM). Based on trichome morphology, the cultivated variety and each of the wild species were seen to have two glandular and two non-glandular trichome types. We classified the eighteen potato species into four groups using trichome type and density criteria. Groups I and II represented species with a higher density of glandular or non-glandular trichomes, respectively, on both abaxial and adaxial leaf surfaces. Group III represented species with a higher density of non-glandular trichomes on abaxial leaf surfaces alone. Group IV represented species with an overall lower trichome density on both abaxial and adaxial leaf surfaces, but which was formed of both glandular and non-glandular types. Honey dew spots were quantified following infestation with the aphid Macrosiphum euphorbiae to test whether trichome composition is associated with resistance to aphid feeding. Fewer honey dew spots were observed in the Group I representative species S. berthaultii and S. hougasii compared to that in species from other groups. Furthermore, correlation coefficient analysis showed that honey dew spot number was negatively associated with glandular trichome density. These results imply that glandular trichomes play an important role in aphid resistance and thus can be used for developing insect-resistant potato.

Levels of Intra-specific AFLP Diversity in Tuber-Bearing Potato Species with Different Breeding Systems and Ploidy Levels.

DNA-based marker analysis of plant genebank material has become a useful tool in the evaluation of levels of genetic diversity and for the informed use and maintenance of germplasm. In this study, we quantify levels of amplified fragment length polymorphism (AFLP) in representative accessions of wild and cultivated potato species of differing geographic origin, ploidy, and breeding system. We generated 449 polymorphic AFLP fragments in 619 plants, representing multiple plants (16–23) from 17 accessions of 14 potato taxa as well as single plants sampled from available accessions (from 3 to 56) of the same 14 taxa. Intra-accession diversities were compared to those of a synthetic ‘taxon-wide’ population comprising a single individual from a variable number of available accessions of each sampled taxon. Results confirm the expected considerably lower levels of polymorphism within accessions of self-compatible as compared to self-incompatible taxa. We observed broadly similar levels of ‘taxon-wide’ polymorphism among self-compatible and self-incompatible species, with self-compatible taxa showing only slightly lower rates of polymorphism. The most diverse accessions were the two cultivated potato accessions examined, the least diverse being the Mexican allohexaploids Solanum demissum and S. iopetalum. Generally allopolyploid self-compatible accessions exhibited lower levels of diversity. Some purported self-incompatible accessions showed relatively low levels of marker diversity, similar to the more diverse self-compatible material surveyed. Our data indicate that for self-compatible species a single plant is highly representative of a genebank accession. The situation for self-incompatible taxa is less clear, and sampling strategies used will depend on the type of investigation. These results have important implications for those seeking novel trait variation (e.g., disease resistance) in gene banks as well as for the selection of individuals for genomics studies. We also show that AFLPs, despite having been largely replaced by other marker types, is highly suitable for the evaluation of within and between accession diversity in genebanks.

Subfunctionalization of duplicate MYB genes in Solanum commersonii generated the cold-induced ScAN2 and the anthocyanin regulator ScAN1.

Wild potato species are useful sources of allelic diversity and loci lacking in the cultivated potato. In these species, the presence of anthocyanins in leaves has been associated with a greater tolerance to cold stress. However, the molecular mechanisms that allow potatoes to withstand cold exposure remain unclear. Here, we show that the expression of AN2, a MYB transcription factor, is induced by low temperatures in wild, cold-tolerant Solanum commersonii, and not in susceptible Solanum tuberosum varieties. We found that AN2 is a paralog of the potato anthocyanin regulator AN1, showing similar interaction ability with basic helix-loop-helix (bHLH) co-partners. Their sequence diversity resulted in a different capacity to promote accumulation of phenolics when tested in tobacco. Indeed, functional studies demonstrated that AN2 is less able to induce anthocyanins than AN1, but nevertheless it has a strong ability to induce accumulation of hydroxycinnamic acid derivatives. We propose that the duplication of R2R3 MYB genes resulted in subsequent subfunctionalization, where AN1 specialized in anthocyanin production and AN2 conserved the ability to respond to cold stress, inducing mainly the synthesis of hydroxycinnamic acid derivatives. These results contribute to understanding the evolutionary significance of gene duplication on phenolic compound regulation.

Determination of virulence contribution from Phytophthora infestans effector IPI-O4 in a resistant potato host containing the RB gene

Late blight of potato, caused by the oomycete pathogen Phytophthora infestans, is persistent and costly disease of this important crop plant. Breeders have continually struggled with the evolution and introduction of new pathogen genotypes that threaten to overcome major resistance genes incorporated into new varieties. Wild species relatives of potato have been a valuable resource for the identification of novel resistance genes including the RB gene, from the diploid wild potato species Solanum bulbocastanum. The RB gene confers partial resistance to most P. infestans genotypes through its recognition of members of the corresponding pathogen effector protein family IPI-O. Multiple alleles are present at the IPI-O locus and while some alleles are recognized by RB to elicit host resistance (e.g. IPI-O1, IPI-O2), others are able to elude detection (e.g. IPI-O4). In our previous research, we found that in planta expression of P. infestans effector IPI-O4 is able to suppress the HR elicited by IPI-O1 in the presence of RB. Additionally, we have observed that P. infestans lineages containing IPI-O4 are able to cause more disease on RB plants compared to those without IPI-O4. This led to a hypothesis that the presence of IPI-O4 results in suppression of RB. In this study, we provide evidence that in planta over-expression of IPI-O4 is able to suppress RB-mediated resistance, causing enlarged lesions in RB containing K41 potato lines. The results of this study indicate that even subtle effects from host or pathogen factors during the early stages of infection can heavily influence the ultimate outcome of the interaction.

Influence of altitude and enhanced ultraviolet-B radiation on tuber production, seed viability, leaf pigments and morphology in the wild potato species Solanum kurtzianum Bitter & Wittm collected from an elevational gradient

Climate change could lead to an upward shift in plant distribution, exposing populations to higher levels of ultraviolet (UV)-B radiation. In the framework of an in situ strategy for conserving potato wild relatives, we evaluated the effect of high UV-B levels on natural population of Solanum kurtzianum. The hypothesis is that plants from naturally higher altitudes are more adapted to increased UV-B radiation. Two populations from low and high altitudes were field supplemented using UV-B-lamps (+UV-B) or excluded from it with plastic filters. Additionally, to assess in which extent the plant responses to these artificial experimental conditions are reproducible in natural conditions, three genotypes were cultivated in two mountain experimental gardens (EG) at different elevations. +UV-B treatment induced changes in leaf morphology and increases in phenolic compounds in both populations, indicating plant adaptation, since chlorophylls and reproductive structures were not negatively affected. These results indicate that this environmental factor may not limit the displacement of populations towards sites with higher UV-B levels. Meanwhile, in higher-altitude EG a tubers yield reduction, mainly through a decreased tuber number and a bigger accumulation of phenolic compounds than in +UV-B treatment were observed, suggesting that UV-B is not the only factor involved in plants adaptation to high altitude environments.

Are We Getting Better at Using Wild Potato Species in Light of New Tools?

Potato (Solanum tuberosum L.), mankind's third most consumed food crop, originated as an interspecific hybrid in the Andean highlands. More than 100 species closely related to potato exist throughout Central and South America. Potato was introduced to Europe, Asia, and North America in the 16th and 17th centuries, but most cultivars were destroyed by late blight epidemics in the mid‐19th century. Late blight resistance genes from the wild relative Solanum demissum Lindl. were subsequently introduced into cultivated potato. Thus, a precedent for the use of wild relatives in potato genetic improvement was established a century ago. Intensive efforts have been made to collect and maintain wild relatives of potato in public germplasm repositories. Genetic diversity in these species is high, and most are sexually compatible with cultivated potato. Perhaps more than any other vegetable crop, potato can benefit from the introgression of genes for valuable traits from wild relatives. However, a century of breeding has realized that potential on only a few notable occasions. Important examples include improved processing quality and resistance to viruses and nematodes. Substantial barriers prevent the facile incorporation of genetic material from wild relatives into potato cultivars. Overcoming these barriers may require an expansion of germplasm collections to include well‐characterized individuals as a complement to population‐based accessions. To be most useful for potato improvement, individual wild species plants will need to be cataloged by allelic composition, haplotype, biochemical properties, and physiological responses to stress. Effectively using the genetic diversity in wild relatives is likely to rely heavily on alternative methods of potato breeding, augmenting reassortment, and selection at the tetraploid level with diploid breeding and genetic modification using biotechnology.

Wading Into the Gene Pool: Progress and Constraints Using Wild Species

Wading Into the Gene Pool: Progress and Constraints Using Wild Species

Genetic and Pathogenic Diversity of Ralstonia solanacearum Causing Potato Brown Rot in China

Causing potato brown rot, Ralstonia solanacearum (R. solanacearum) strains are reported as one of the most destructive bacteria to potato (Solanum tuberosum L.) in China. In this study, 113 strains were isolated from potato, collected in the four major agroecological zones in China. The study showed that 102 strains belonged to the phylotype IIB sequevar 1 (race 3 biovar 2). The 11 remaining strains belonged to the phylotype I, sequevar 13, 17, 18, 16 or 14 M, a new sequevar closely related to sequevar 14. Thirty-four strains were further characterized according to their virulence at low temperature on three wild potato species. IIB-1 strains all belonged to high and moderate virulence, while others belonged to the low virulence group, which had limited pathogenicity.

Phytophthora infestans Effectors IPI-O1 and IPI-O4 Each Contribute to Pathogen Virulence.

Potato late blight, caused by the oomycete pathogen Phytophthora infestans, is one of the most destructive plant diseases. Despite decades of intensive breeding efforts, it remains a threat to potato production worldwide, because newly evolved pathogen strains have overcome major resistance genes quickly. The RB protein, from the diploid wild potato species Solanum bulbocastanum, confers partial resistance to most P. infestans strains through its recognition of members of the corresponding pathogen effector protein family IPI-O. IPI-O comprises a multigene family and while some variants are recognized by RB to elicit host resistance (e.g., IPI-O1 and IPI-O2), others are able to elude detection (e.g., IPI-O4). IPI-O1 is almost ubiquitous in global P. infestans strains while IPI-O4 is more rare. No direct experimental evidence has been shown to demonstrate the effect of IPI-O on pathogen virulence in the P. infestans-potato pathosystem. Here, our work has demonstrated that in planta expression of both IPI-O1 and IPI-O4 increases P. infestans aggressiveness resulting in enlarged lesions in potato leaflets. We have previously shown that IPI-O4 has gained the ability to suppress the hypersensitive response induced by IPI-O1 in the presence of RB. In this study, our work has shown that this gain-of-function of IPI-O4 does not compromise its virulence effect, as IPI-O4 overexpression results in larger lesions than IPI-O1. We have also found that higher expression of IPI-O effectors correlates with enlarged lesions, indicating that IPI-O can contribute to virulence quantitatively. In summary, this study has provided accurate and valuable information on IPI-O's virulence effect on the potato host.

Non‐GMO potato lines with an altered starch biosynthesis pathway confer increased‐amylose and resistant starch properties

The lack of a gene marker directly affecting starch biosynthesis in the potato tuber is documented. The absence of a 454 bp amplified fragment length polymorphism (AFLP) Solanum tuberosum fragment was identified in the wild potato species Solanum sandemanii and its absence results in a combined increased‐amylose/high‐sugar tuber chemotype. The trait is recessive, termed IAm (Increased Amylose) and was transferred to modern tetraploid S. tuberosum potato cultivars by marker‐assisted crossing. Compared to controls, IAm plants had a larger number of stems and air exposed stolons, their tubers were smaller, elongated, and they were irregularly shaped. IAm starch had 28–59% higher amylose content than control starch, the starch granules were small and grossly misshaped, they had reduced crystallinity, swelling, and viscosity, reduced in vitro digestion rates with increased resistant starch fraction. The primary gene(s) responsible for the IAm phenotype is not known, but increased granule‐associated phosphorylase (Pho1) and reduced starch synthase (SS) protein and enzyme activity in the IAm plants might explain the effects on starch structure. The data support the establishment of non‐genetically modified crops with health‐related slowly digestible carbohydrate.

BC1 and F1 Progeny from Solanum × michoacanum (+) S. tuberosum Somatic Hybrids, Autofused 4× S. michoacanum and Cultivated Potato

Solanum×michoacanum (mch) is a valuable source of resistance to Phytophthora infestans and has not been used in potato breeding due to crossing barriers with S. tuberosum. Somatic hybridization followed by backcrossing is a strategy for introgression of important traits from wild potato species sexually isolated from S. tuberosum. Tetraploid somatic hybrids Solanum×michoacanum (+) S. tuberosum [mch (+) tbr] and autofused 4× mch lines were crossed to several potato cultivars as male and female parents. Our results indicate that resistance against late blight, originating from mch (+) tbr somatic hybrids and autofused 4× mch lines can be transferred to cultivated potato by sexual crossing. Viable and fertile progeny was obtained providing a route to using mch as a source of resistance to P. infestans in potato breeding.